1. Field of the Invention.
The present invention relates to fryers and more particularly to filtration systems for such fryers.
2. Description of Related Art.
Commercial "deep fat" fryers used in restaurants and other institutions contain several gallons of oil which is heated to a high temperature to fry various foods such as french fries, chicken and fish. Typically, the same oil is used over and over again until it deteriorates to an extent which requires replacement of the oil. Deterioration is caused by contact with the air and the carbonization of food particles retained in the oil. To extend the life of the oil, the oil may be filtered on a regular basis which counteracts the deterioration of the oil.
Two primary types of oil filters used today for deep fat fryers are manual and mechanical filters. In essence, manual oil filters are sophisticated straining devices. They include a mesh netting carried by a wire frame. In use, the oil is removed first from the fryer heating vessel, and is then poured through the manual filter into a larger container, filtering the oil as it passes through the filter. The oil is then manually returned to the fryer from the large container.
In mechanical filters, the oil is transferred (typically by gravity flow) to a vessel containing a filter and the filtered oil is returned to the fryer usually by means of a pump. One advantage of mechanical filters is that the operator's contact with the oil which can be quite hot is minimized. In addition, the oil's contact with the air is also minimized. Still further, mechanical filters are usually faster and more efficient than manual filters.
However, mechanical filters are also typically considerably more expensive than manual filters. In one prior design, a mechanical filter is built into each fryer. In a kitchen having several fryers, the added cost of a mechanical filter for each fryer can be substantial. To reduce the cost of the filters, some prior designs have used a single built-in filter which is shared by more than one fryer. Such systems usually have a number of conduits and valves between the filter and the various fryers, for selectively transporting the oil back and forth between the fryers and the filter. However, in order to minimize the length of such conduits, it is usually necessary to place the fryers side by side and to limit the total number of fryers connected to any one filter.
Another type of mechanical filter, the portable filter, does not impose these limitations. A portable filter, which is usually transported upon a wheeled cart, may be moved from fryer to fryer to filter the oil at each fryer in turn, allowing the servicing of all the fryers in the kitchen regardless of the placement of the fryers. To filter the oil of a particular fryer, the filter is wheeled underneath the vessel of the fryer and the used oil is allowed to drain by gravity flow through a filter into a holding vessel in the portable filter. A pump pumps the filtered oil back to the fryer heating vessel through a flexible hose (typically referred to as a "wand"), the outlet of which is placed into the fryer vessel.
One disadvantage of portable filters is that the use of the flexible hose or wand to return the hot oil to the fryer increases the chance of contact of the hot oil with the operator. In addition, the portable filter can obstruct aisles while it is placed in front of a fryer to perform the filtration operation.
In addition, some portable filters require a separate storage area. In some prior designs, the fryer and portable filter are designed in a manner which allows the portable filter to be stored underneath the fryer. However, because of the external wand, the portable filter typically cannot be enclosed completely within the fryer while the filtration operation is in progress. Moreover, it is often necessary to provide a wall power outlet in the vicinity of each fryer to power the portable filter.